Why Email Agents Demand Idempotency: Lessons from Real-World Failures

Email agents demonstrate idempotency challenges in the most visible way—duplicate messages landing in a user's inbox instead of hidden as database rows. The core principle is that webhook systems guarantee at-least-once delivery, not exactly-once, making duplicate handling a design requirement rather than an edge case. Implementing atomic deduplication, distributed locking, and proper acknowledgment patterns is essential for building reliable event-driven systems.